Dental caries is characterized by dissolution of the mineral portion of the tooth, which can result in pain and loss of viability of the tooth, necessitating costly repair or extraction of the tooth. Dental caries affects 50% of children aged 5-9 years, 67% of adolescents age 12-17 years, and 94% of adults aged ≧18 years in the US (Morbidity and Mortality Weekly Reports 51: 144-147, 2002). Clean teeth will not decay; however, even with vigorous cleaning it is difficult to keep teeth sufficiently clean. Various methods have been developed to prevent or alleviate dental caries including, for example, the addition of sodium fluoride, sodium silicofluoride or hydrofluosilicic acid to drinking water, and sodium fluoride or tin fluoride to topical preparations, including dentifrices and mouthrinses. The prevention of caries by coating teeth with polymeric materials or sealants has been used; however, these techniques are costly, can require etching of the teeth with phosphoric acid and can be effective only in young children who have not yet developed caries. Antibacterial agents, including antibiotics, have also been proposed as a treatment for dental caries. Antibiotics kill microorganisms that are responsible for producing acid in the mouth such as Streptococcus mutans, but antibiotics are not selective in the killing of oral bacteria and also kill beneficial bacteria present in the oral cavity. This can result in a microbial imbalance in the mouth, which can have serious consequences. Therefore, more effective methods for the treatment and prevention of dental caries are needed in the art.
Actinobacillus actinomycetemcomitans (Aa) is the principal etiologic agent of early-onset periodontitis including localized and generalized prepubertal periodontitis, localized and generalized juvenile periodontitis, and rapidly progressive or refractory adult periodontitis. Tooth loss is the ultimate detrimental effect of destructive periodontal disease. A national survey of the United States revealed a prevalence of localized juvenile periodontitis of 0.53% and of generalized juvenile periodontitis of 0.13%. Loe & Brown, J. Periodontol. 62:608-616 (1991). Findings from a number of studies corroborate the conclusion that early-onset disease is similar in other industrialized countries and is more frequent in developing countries. Loe & Brown, J. Periodontol. 62:608-616 (1991).
In addition, certain types of adult periodontitis, which in general are very common conditions affecting over half the adult population, are likely to be caused by a select group of microorganisms indigenous to the oral cavity. These include Aa, Porphyronzonas gingivalis, Prevotella intermedia, Bacteroides forsythus, Treponema denticola, Campylobacter rectus and Eikenella corrodens. 
There are antibiotic, surgical, and mechanical therapies for the treatment of the various types of periodontitis, but no means for prevention. Tetracycline has been widely used in the treatment of early-onset periodontitis. There remains a concern, however, of strains developing resistance to tetracycline as well as the possibility of overgrowth of other pathogenic microorganisms. Given the incidence of periodontal diseases, safe preventative and treatment strategies are needed in the art. Control of periodontal disease is also very important in light of recent attention to the possible role of periodontal infections as risk factors for systemic disease (e.g., coronary heart disease). Therefore, methods of treatment and prevention of early-onset periodontitis, localized and generalized juvenile periodontitis, and rapidly progressive or refractory adult periodontitis are needed in the art.